Russians sold RD-180 with technology to reproduce them in USA. It was just too expensive to make them in America, so eventually Energomash got all orders to make them for Atlases. And now Falcons are pretty good too, so less need in RD-180 - Orbital still buys RD-181, single chamber engine though. And Raptors could be in use soon. And BE-4 from Blue Origin hopefully will power new ULA Vulcan rockets soon too... and that oxygen-resisting metallurgy is likely used at least in some of them (RD-181 for sure).